Alkylation process and catalyst therefor

ABSTRACT

A composition of matter comprises trifluoromethanesulfonic acid on a solid support material which contains boron phosphate and/or boron sulfate. Preferred support materials are boron phosphate, boron phosphate-coated silica and boron sulfate-coated silica. The above composition is used as a catalyst for alkylating at least one C2-C7 alkane (preferably isobutane or an isopentane) with at least one C2-C7 alkene (preferably butene-2).

This application is a division of Ser. No. 07/973,493, filed Nov. 9,1992 and now U.S. Pat. No. 5,233,199.

BACKGROUND OF THE INVENTION

In one aspect, this invention relates to a novel composition of matter,which is effective as an alkylation catalyst, comprisingtrifluoromethanesulfonic acid and an inorganic solid support material.In another aspect, this invention relates to the alkylation of alkanes(paraffins) with alkenes (monoolefins), in the presence of a novel solidcatalyst composition comprising trifluoromethanesulfonic acid and asolid support material.

The use of supported trifluoromethanesulfonic acid catalyst for thealkylation of alkanes with alkenes is known and has been described inthe patent literature (e.g., in European Patent Application havingPublication No. EP 0 433 954 A1). The present invention is directed to anovel, effective alkylation catalyst composition comprisingtrifluoromethanesulfonic acid and specific inorganic support materials,and to the use of said catalyst composition in an alkylation process.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a novel solid compositionof matter which is active as an alkylation catalyst. It is anotherobject of this invention to alkylate alkanes with alkenes in thepresence of a novel solid catalyst comprising trifluoromethanesulfonicacid and an inorganic support material. Other objects and advantageswill be apparent from the detailed description of the appended claims.

In accordance with this invention, a composition of matter (effective asa catalyst for alkylating alkanes with alkenes) comprisestrifluoromethanesulfonic acid and a solid support material comprising atleast one boron compound selected from the group consisting of boronphosphate and boron sulfate. Preferably, this composition of matterconsists essentially of trifluoromethanesulfonic acid and boronphosphate. In another preferred embodiment, the composition of matter ofthis invention consists essentially of trifluoromethanesulfonic acid andboron phosphate-coated silica. In a further preferred embodiment, thecomposition of this invention consists essentially oftrifluoromethanesulfonic acid and boron sulfate-coated silica.

Also in accordance with this invention, a process for alkylating alkanescomprises the step of contacting at least one feed alkane (i.e., atleast one straight-chain alkane or at least one branched alkane or amixture thereof) containing about 2-7 carbon atoms per molecule with atleast one feed alkene (i.e., at least one straight chain alkene or atleast one branched alkene or a mixture thereof) containing about 2-7carbon atoms per molecule with the above-described catalyst compositioncomprising trifluoromethanesulfonic acid and at least one solid supportmaterial comprising boron phosphate and/or sulfate, at effectivealkylation conditions so as to obtain at least one product alkanecontaining at least two more carbon atoms per molecule than said atleast one feed alkane.

DETAILED DESCRIPTION OF THE INVENTION

The composition of matter of this invention comprises CF₃ SO₃ H on aninorganic support material which contains BPO₄ and/or B₂ (SO₄)₃.Generally, the support material contains about 20 to about 100 weight-%BPO₄ and/or B₂ (SO₄)₃ and up to about 80 weight-% (preferably about0.5-80 weight-%) SiO₂. Other inorganic solids, such as alumina andactivated carbon, may be used in lieu of or in addition to silica. TheBET/N₂ surface area of these support materials generally is in the rangeof about 200 to about 400 m² /g. Preferably, the particles of thecomposition of matter have a size in the range of smaller than 20 meshand larger than 40 mesh.

The composition of matter of this invention can be prepared in anysuitable manner. Preferably, the BPO₄ -containing support material isprepared by the reaction of a boric acid ester B(OR)₃ wherein each R canbe independently selected from alkyl radicals containing 1-5 carbonatoms (more preferably tri-n-propyl borate) and orthophosphoric acid (H₃PO₄), with SiO₂ either being absent during this reaction (so as toprepare a 100% BPO₄ material) or SiO₂ being present during this reactionin an amount as to provide a material containing up to about 80 weight-%SiO₂ (preferably about 0.5-80 weight-% SiO₂). When a B₂ (SO₄)₃-containing support material is used, it is preferably prepared by thereaction of a boric acid ester (such as tri-n-propyl borate) andsulfuric acid, either in the absence of or in the presence of up to 80weight-% SiO₂ (preferably about 0.5-80 weight-% SiO₂). The thus-obtainedsupport material is then preferably calcined (generally for about 2-5hours at a temperature of about 250°-500° C., either in air or in a N₂atmosphere). The CF₃ SO₃ H catalyst component can be applied to thesupport material in any suitable manner. Generally, it is added inliquid form to the top layer of the solid support material (preferablybeing present in a catalyst bed) just prior to the alkylation reaction,generally at a weight ratio of CF₃ SO₃ H to said support material in therange of about 0.02:1 to about 0.4:1.

The solid compositions or matter described above are employed ascatalysts in the alkylation process of this invention. The process foralkylating C₂ -C₇ alkanes (preferably isoalkanes, i.e., branchedalkanes) with C₂ -C₇ alkenes (preferably those containing an internaldouble bond) can be carried out in any suitable manner. The contactingof a mixture of at least one feed alkane and at least one feed alkene,generally at a molar alkane/alkene ratio of about 6:1 to about 12:1(preferably about 8:1 to about 10:1), with one of the above-describedcatalyst compositions can be carried out at effective alkylationconditions, preferably at a relatively low temperature of up to about100° C., preferably about -10° to about 100° C., more preferably about0°-30° C., most preferably about 0°-5° C., preferably at a pressure ofabout 2-6 atm.

The alkane/alkene feed mixture can be contacted with the catalystcomposition in any suitable mode, preferably in a fixed catalyst bedoperation in which the feed mixture flows downward through a solidcatalyst layer, generally at a liquid hourly space velocity of about0.5-5 (preferably about 1-3) cm³ alkane/alkene feed per cm³ catalystcomposition per hour. The alkylation process can be carried out in acontinuous manner or as a batch process. Generally, the CF₃ SO₃ Hcomponent moves as a zone along the solid catalyst bed in the directionof the alkylation feed. When the CF₃ SO₃ H zone approaches the exitregion of the catalyst bed, the reactant flow can be reversed (so thatthe CF₃ SO₃ H zone can travel back through the catalyst bed).

Suitable feed alkanes are normal (straight chain) alkanes and isoalkanes(i.e., branched) alkanes, each containing 2-7 carbon atoms per molecule.Non-limiting examples of suitable alkanes are propane, n-butane,isobutane, n-pentane, isopentanes (2-methylbutane and2,2-dimethylpropane), n-hexane, isohexanes (such as 2-methylpentane,3-methylpentane, 2,2-dimethylbutane), n-heptane and isoheptanes (such asmethyl-substituted hexanes and dimethyl-substituted pentanes). Presentlypreferred are C₃ -C₆ alkanes, more preferably branched C₄ -C₆ alkanes.Particularly preferred feed alkanes are isobutane and 2-methylbutane.

Suitable feed alkenes are normal (straight chain) and branched alkenescontaining one C═C double bond and 2-7 carbon atoms per molecule,preferably those containing an internal C═C double bond (more preferablyin the 2 position). Non-limiting examples of suitable alkenes arepropylene, butene-1, butene-2, isobutylene, pentene-1, pentene-2,isopentenes, hexene-1, hexene-2, hexene-3 and isohexenes. Preferredalkenes are those containing 3-5 carbon atoms per molecule. Thepresently more preferred feed alkene is butene-2.

The alkylation process of this invention generally generates a multitudeof hydrocarbon products containing a greater number of carbon atoms permolecule than the feed alkane(s), as is demonstrated in the examples.Thus, it is generally necessary to separate the various formedhydrocarbon products from one another and from unconverted feedhydrocarbons. This separation can be carried out in any suitable manner,generally by fractional distillation (possibly in the presence of anextractant, i.e., by extractive distillation), as can be determined bypersons skilled in the various liquid-liquid separation technologies.

The following examples are provided to further illustrate the processesof this invention, and are not to be construed as unduly limiting thescope of this invention.

EXAMPLE I

This example illustrates the preparation of several solidboron-containing catalyst support materials.

Boron phosphate (BPO₄) was prepared by adding, with stirring over aperiod of about 3 hours, 93.22 grams of tri-n-propyl borate (normalboiling point: 175°-177° C.; obtained from Aldrich Chemical Company,Milwaukee, Wis.) to 54.82 grams of a aqueous phosphoric acid (containingabout 85 weight-% H₃ PO₄ and 15 weight-% H₂ O) in a 3-neck flask, atabout 80° C. under a nitrogen gas atmosphere. The reaction mixture washeated under reflux conditions to a temperature of about 120° C.Thereafter, essentially all liquids (mainly water and formed propanol)were distilled off. The white solid residue of BPO₄ was vacuum-dried ata temperature of about 120° C. for 3 hours. 25.5 grams of dry boronphosphate (B:P atomic ratio 1.04:1) was obtained.

BPO₄ /SiO₂ A, containing 27 weight-% BPO₄, was prepared as follows.34.35 grams of calcined 20-40 mesh silica (BET/N₂ surface area:347 m²/g; obtained from Davison Chemical Division of W. R. Grace and Co.,Baltimore, Md.) and 13.8 grams of a mixture of 85 weight-% H₃ PO₄ PG,8and 15 weight-% H₂ O were placed into a 3 neck glass flask. The mixturewas heated to about 80° C. under a N₂ atmosphere, and 22.70 gtri-n-propyl borate was added dropwise, with stirring, to the abovemixture. The entire reaction mixture was heated for 2 hours under refluxconditions. Thereafter, essentially all liquids (mainly propanol andwater) were distilled off at a temperature of about 120° C. The solidresidue was dried for 3 hours at a temperature of about 150° C. undervacuum conditions. 48.05 g of dry BPO₄ on SiO₂ (containing 27 weight-%BPO₄) was obtained.

BPO₄ /SiO₂ B, containing 75 weight-% BPO₄, was prepared essentially inaccordance with the above-described procedure for BPO₄ /SiO₂ A, exceptthat the amount of added silica was adjusted to about 25 weight-% SiO₂of the support material (in lieu of 73 weight-% of SiO₂ used in BPO₄/SiO₂ A) and that BPO₄ /SiO₂ B had been heated for 2 hours at 300° C. inair.

B₂ (SO₄)₃ /SiO₂ A, containing 35 weight-% B₂ (SO₄)₃, was prepared asfollows. 22.70 grams of (0.121 mole) of tri-n-propyl borate, 17.76 gramsof 100% H₂ SO₄ and 34.35 grams of silica (described in Example I weremixed and heated, with stirring, for about 2 hours at 80° C. Thereafter,the reaction mixture was heated to 120° C., and liquids (mainly formedpropanol) were distilled off. The dry pink solid residue was calcined inair at 275° C. for 2 hours.

B₂ (SO₄)₃ /SiO₂ B, containing 70 weight-% B₂ (SO₄)₃, was preparedessentially as described above for B₂ (SO₄)₃ /SiO₂ A, except that theweight of silica was adjusted to provide 30 weight-% of SiO₂ in thefinished catalyst (in lieu of 65 weight-% SiO₂).

EXAMPLE II

This example illustrates the use of the catalysts comprisingtrifluoromethanesulfonic acid and the solid support materials describedin Example I.

Each of the five materials described in Example I and silica (as controlsupport material) were ground and sieved. Particles having a mesh sizeof smaller than 20 but larger than 40 were calcined at about 500° C. forabout 2-21/2 hours. A U-shaped stainless steel reactor tube (innerdiameter: 0.29 inch; length: 60 inches) was filled with one of the abovematerials. About 6.6 grams (3.9 cm³) of trifluoromethanesulfonic acidwas then added to the top (entrance) zone of the packed column. Theentire column was maintained at a temperature of about 0° C., and aliquid alkylation feed of 10 weight-% butene-2 (containing approximatelyequal amounts of cis and trans isomers) and 90 weight-% isobutane werepumped through the packed column at a rate of 1 cm³ per minute. Theexiting alkylation product was analyzed about every 60 minutes by meansof a gas chromatograph. Each test lasted about 50-60 hours. Average testresults are summarized in Table I.

                                      TABLE I                                     __________________________________________________________________________                         Alkylate                                                                % Olefin                                                                            Product Composition                                                                        Alkylate                                    Catalyst       Conversion                                                                          C5 C6                                                                              C7                                                                              C8 C9+                                                                              Octane No..sup.6                            __________________________________________________________________________    CF.sub.3 SO.sub.3 H on SiO.sub.2.sup.1                                                       99.6  14.5                                                                             6.2                                                                             5.4                                                                             54.8                                                                             9.9                                                                              92.8                                        CF.sub.3 SO.sub.3 H on BPO.sub.4                                                             98.5  10.3                                                                             4.4                                                                             4.4                                                                             70.7                                                                             5.0                                                                              94.6                                        CF.sub.3 SO.sub.3 H on BPO.sub.4 /SiO.sub.2 A.sup.2                                          97.8  15.5                                                                             5.9                                                                             5.0                                                                             60.4                                                                             6.1                                                                              93.3                                        CF.sub.3 SO.sub.3 H on BPO.sub.4 /SiO.sub.2 B.sup.3                                          99.4  11.3                                                                             5.4                                                                             5.5                                                                             62.1                                                                             10.0                                                                             92.8                                        CF.sub.3 SO.sub.3 H on B.sub.2 (SO.sub.4).sub.3 /SiO.sub.2 A.sup.4                           100   4.6                                                                              3.7                                                                             4.5                                                                             71.2                                                                             14.4                                                                             93.6                                        CF.sub.3 SO.sub.3 H on B.sub.2 (SO.sub.4)/SiO.sub.2 B.sup.5                                  99.8  12.0                                                                             5.4                                                                             5.4                                                                             61.8                                                                             6.0                                                                              92.9                                        __________________________________________________________________________     .sup.1 BET/N.sub.2 surface area: about 347 m.sup.2 /g (described in           Example I)                                                                    .sup.2 containing 27 weight% BPO.sub.4                                        .sup.3 containing 75 weight% BPO.sub.4                                        .sup.4 containing 35 weight% B.sub.2 (SO.sub.4).sub.3                         .sup.5 containing 70 weight% B.sub.2 (SO.sub.4).sub.3                         .sup.6 (research octane number + motor octane number) divided by 2       

Test data in Table I clearly show that the amount of desirable C₈hydrocarbon products was greatest in runs employing BPO₄ -containing andB₂ (SO₄)₃ -containing catalyst support materials. The octane numbers ofthe alkylates produced in runs employing BPO₄ -containing and B₂ (SO₄)₃-containing catalyst support materials were generally higher than theoctane number of the alkylate obtained in the CF₃ SO₃ H/SiO₂ run. Anadditional alkylation test (not described in detail herein) was carriedout with a 2-methylbutane/butene-2 feed in the presence of a CF₃ SO₃H/BPO₄ /SiO₂ catalyst, at substantially the same reaction conditions asthose described above.

Reasonable variations, modifications and adaptations for various usagesand conditions can be made within the scope of the disclosure and theappended claims, without departing from the scope of this invention.Also, it is expected that the catalyst materials of this invention willbe active as catalysts for isomerizing alkanes (in particular C₅ -C₈straight-chain and branched alkanes) and cycloalkanes (in particularmethylcyclopentane, which will be isomerized to cyclohexane).

That which is claimed is:
 1. A composition of matter comprisingtrifluoromethanesulfonic acid and a solid material comprising boronphosphate, wherein the weight ratio of trifluoromethanesulfonic acid tosaid solid material is in the range of about 0.02:1 to about 0.4:1.
 2. Acomposition of matter in accordance with claim 1, wherein said solidmaterial consists essentially of boron phosphate.
 3. A composition ofmatter in accordance with claim 1 consisting essentially oftrifluoromethanesulfonic acid and boron phosphate.
 4. A composition ofmatter in accordance with claim 1, wherein said solid material consistsessentially of boron phosphate and about 0.5-80 weight-% silica.
 5. Acomposition of matter in accordance with claim 4, wherein said supportmaterial has been prepared by the reaction of tri-n-propyl borate andorthophosphoric acid in the presence of silica.
 6. A composition ofmatter in accordance with claim 4 consisting essentially oftrifluoromethanesulfonic acid and boron phosphate-coated silica.
 7. Acomposition of matter in accordance with claim 1, wherein said solidmaterial comprises about 20-100 weight-% boron phosphate.
 8. Acomposition of matter comprising trifluoromethanesulfonic acid and asolid material comprising boron sulfate, wherein the weight ratio oftrifluoromethanesulfonic acid to said solid material is in the range ofabout 0.02:1 to about 0.4:1.
 9. A composition of matter in accordancewith claim 8, wherein said solid material consists essentially of boronsulfate.
 10. A composition of matter in accordance with claim 8consisting essentially of trifluoromethanesulfonic acid and boronsulfate.
 11. A composition of matter in accordance with claim 8, whereinsaid solid material consists essentially of boron sulfate and about0.5-80 weight-% silica.
 12. A composition of matter in accordance withclaim 11, wherein said solid material has been prepared by the reactionof tri-n-propyl borate and sulfuric acid in the presence of silica. 13.A composition of matter in accordance with claim 11 consistingessentially of trifluoromethanesulfonic acid and boron sulfate-coatedsilica.
 14. A composition in accordance with claim 8, wherein said solidmaterial comprises about 20-100 weight-% boron sulfate.
 15. Acomposition of matter comprising trifluromethanesulfonic acid and asolid material comprising boron phosphate and boron sulfate, wherein theweight ratio of trifluoromethanesulfonic acid to said solid material isin the range of about 0.02:1 to about 0.4:1.
 16. A composition inaccordance with claim 15, wherein said solid material consistsessentially of boron phosphate and boron sulfate.
 17. A composition inaccordance with claim 15 consisting essentially or trifluoromethanesulfonic acid, boron phosphate and boron sulfate.
 18. A composition inaccordance with claim 15, wherein said solid material consistsessentially of boron phosphate, boron sulfate and about 0.5-80 weight-%silica.
 19. A composition in accordance with claim 18 consistingessentially of trifluoromethanesulfonic acid, boron phosphate, boronsulfate and silica.
 20. A composition in accordance with claim 15,wherein the combined weight percentage of boron phosphate and boronsulfate in said solid material is about 20-100.